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Bulletin 2 



Structural Materials Research Laboratory 

Lewis In s titu te 

Chicago 



Effect of Curing Condition on 

the Wear and Strength 

of Concrete 

By 

DUFF A. ABRAMS 

Professor in Charge of Laboratory 



(Authorized Reprint from the Proceedings of the 
American Rail-way Engineering Association, Vol. 20, 1919) 



Published by the 

STRUCTURAL MATERIALS RESEARCH LABORATORY 

Third Printing, September, 1922 






m*wi* 



RESEARCHES in the properties of concrete and concrete mate- 
- rials at the Structural Materials Research Laboratory are being 
carried out through the cooperation of the Lewis Institute and the 
Portland Cement Association, Chicago. The research work has been 
under way since September 1, 1914. 

The control of the policies of the Laboratory is vested in an 
Advisory Committee, consisting of representatives of the Lewis 
Institute and the Portland Cement Association, as follows : 

Lewis Institute : 
GEO. N. CARMAN, Director of Lewis Institute. 
DUFF A. ABRAMS, Professor in Charge of Laboratory. 

Portland Cement Association: 
F. W. KELLEY, Chairman, Technical Problems Committee, Albany, N.Y. 
ERNEST ASHTON, Member, Technical Problems Committee, Allen- 
town, Pa. 

The investigations are being carried out by a staff of engineers, 
chemists, and assistants who give their entire time to this work. The 
results of these researches are published in the form of papers before 
engineering and technical societies and in Circulars and Bulletins 
issued by the Laboratory. 



Bulletin 2 

Structural Materials Research Laboratory 

Lewis Institute 

Chicago 



Effect of Curing Condition on 

the Wear and Strength 

of Concrete 



DUFF A. ABRAMS 

M 

Professor in Charge of Laboratory 



(Authorized Reprint from the Proceedings of the 
American Rail-way Engineering Association, Vol. 20, 1910) 



Published by the 

STRUCTURAL MATERIALS RESEARCH LABORATORY 

Third Printing, September, 1922 






FOREWORD 



This paper was first published as a part of the Eeport of the 
Committee on Masonry of the American Railway Engineering 
Association (Proceedings, Vol. 20, 1919). It was reprinted as 
Bulletin 2 of this Laboratory in May, 1919. A second printing 
was necessary in December, 1920. At that time a few minor 
errors were corrected and the bibliography was brought up to 
date by the addition of a number of references which did not 
appear in the original report. 

A third printing is now necessary. A few footnotes have 
been added which show departures of present practice from that 
followed in the tests. The bibliography has been again revised. 

Acknowledgment is made to the American Railway Engi- 
neering Association for permission to reprint this paper in bulletin 
form. 



EFFECT OF CURING CONDITION ON THE WEAR 
AND STRENGTH OF CONCRETE 

By Duff A. Abrams. 
Introduction. 

The necessity for careful restriction on the quantity of mixing water 
used in concrete, and the importance of proper curing conditions during 
the period of setting and hardening are not generally appreciated by 
engineers and contractors doing concrete work. In view of the wide- 
spread use of concrete in the construction of pavements, floors, loading 
platforms, and in other places requiring high strength and resistance to 
abrasion, it seemed desirable to carry out an experimental study which 
would bring out the effect of water content and curing conditions on 
the compressive strength and the wearing resistance of concrete, and the 
relation between these two properties. 

These tests were made as a part of the experimental studies of the 
properties of concrete and concrete materials, being carried out through 
the cooperation of Lewis Institute and the Portland Cement Association 
at the Structural Materials Research Laboratory. 

This series comprised compression tests of 120 6 by 12-in. cylinders and 
wear tests on 300 blocks, 8 in. square and 5 in. in thickness. A 1 : 4 mix 
was used throughout, that is, 1 volume cement and 4 volumes mixed aggre- 
gate. This mix is about the same as the l:lj4:3 or 1:2:3 mixes generally 
used for concrete which is to withstand high stresses or to form the 
wearing surface of pavements. Most of the tests were made on sand and 
pebble aggregates. One group was repeated with crushed limestone as 
coarse aggregate. 

Concrete of six different consistencies was used, each being stored 
under four different conditions : 

(1) Damp sand 4 months (120 days), tested damp, 

(2) Damp sand 21 days, air 99 days, 

(3) Damp sand 3 days, air 117 days, 

(4) Air of laboratory for entire curing period of 4 months. 
Parallel tests were made throughout on compression and wear. All 

tests were made at the age of 4 months. 

The wear blocks were tested in the Talbot-Jones rattler by the same 
methods that were used in other tests carried out in this Laboratory.* 

Acknowledgment is due to the Chicago Gravel Company, Chicago, 
for their courtesy in furnishing the sand and pebble aggregate used in 
these tests, and to Dolese & Shepard, Chicago, for the crushed limestone. 

*See "A Method of Making Wear Tests of Concrete," by D, A. Abrams, Proc. 
Am. Soc. Testing Mat., Part II, 1916; also "Effect of Time of Mixing on the Strength 
and Wear of Concrete." by D. A. Abrams. Proc. Am. Concrete Ins., 1918. 



Structural Materials Research Laboratory 



Materials. 

The portland cement used in these tests consisted of a mixture of 
equal parts of four brands purchased in the Chicago market. The brands 
were thoroughly mixed by placing one sack of each in a concrete mixer 
and running for about one minute. Complete tests of the cement are 
given in Table 1. 

Table 1 — Tests of Cement. 

The cement consisted of a mixture of equal parts of four brands purchased on the 
Chicago market (Lot No. 3705). 

All tests made in accordance with Standard Specifications and Tests for Portland 
Cement of the American Society for Testing Materials. 

Miscellaneous Tests. 



Fineness 

Residue 

on 200 

Sieve 


Normal 

Consistency 

Per Cent 

by Weight 


Time of Setting 


Soundness 

Test (over 

Boiling 

Water) 


Vicat Needle 


Gillmon 


i Needle 


Initial 


Final 


Initial 


Final 




h. m. 


h. m. 


h. m. 


h. m. 




20.4 


23.0 


4:25 


8:05 


5:10 


8:45 


O.K. 



1:3 standard sand mortar. Mortar Strength Tests. 



Mixing 

Water 

Per 


Tensile Strength of Briquets 
lb. per sq. in. 


Compressive Strength of 2 by 4-in. Cylinders 
lb. per sq. in. 


Cent 


7 da. 


28 da. 


3 mo. 


6 mo. 


1 yr. 


2yr. 


7 da. 


28 da. 


3 mo. 


6 mo. 


lyr. 


2yr. 


10.3 


266 


367 


464 


431 


415 


357 


2080 


3800 


4240 


5130 


5060 


4600 



The aggregates consisted of sand and pebbles from the Chicago 
Gravel Company's plant near Elgin, 111., and crushed limestone from 
Dolese & Shepard Company's quarry. Before using, the sand was screened 
through a No. 4 sieve. All material coarser than this size was rejected. 
The sand was used without further screening, but care was taken to see 
that the material in the bin was thoroughly mixed so that it was uniform 
throughout the series. Pebbles and crushed limestone were screened to 
three different sizes (No. 4-^i, H~Y> and 3 A-l}i in.) and recombined in 
definite proportions for each batch, as shown by the sieve analyses in 
Table 2. 

The mixing and curing water was from the city water supply obtained 
from Lake Michigan. 

The weights per cubic foot of aggregates were determined by means 
of machined, cast-iron measures having capacities of % and Y cu. ft. 
The V& cu. ft. measure was used for the sand and the ^2 cu. ft. for the 
coarse aggregates and the mixed aggregates. The inside diameter of 
each measure is equal to the depth. The test was made by filling the 
measure about one-third full and puddling with a 5/g-in. steel bar pointed 
at the lower end. Filling and puddling were continued in like manner 
until the measure was full. After striking off with a straightedge the 



Effect of Curing Condition of Concrete 



weight was determined. This is the method recommended by Committee 
C-9 on Concrete of the American Society for Testing Materials, but the 
method has not yet been standardized by the Society.* 

Table 2 — Sieve Analysis of Aggregates. 

Sieves manufactured by the W. S. Tyler Company, Cleveland, Ohio. 







Per Cent by Weight Coarser than Each Sieve 


Sieve 
Number 


Size of 
Clear 












Crushed 


Sand 


Sand 


or 


Opening 


Sand 


Pebbles 


Lime- 


and 


and 


Size 


inches 






stone 


Pebbles 


Limestone 


100 


.0058 


98 


100 


100 


99 


99 


48* 


.0116 


90 


100 


100 


96 


96 


28* 


.023 


60 


100 


100 


84 


84 


14* 


.046 


42 


100 


100 


77 


77 


8 


.093 


22 


100 


100 


69 


69 


4 


.185 





100 


100 


60 


60 




.37 

.75 

1.25 




84 

50 




84 

50 




50 
30 




50 




30 


IK 








*(Note added at Third Printing, September, 1922). The No. 48, 28, and 14-mesh 
sieves give the same separation as the No. 50, 30, and 16 now used in the "Tentative 
Method of Test for Sieve Analysis of Aggregates for Concrete" of the American 
Society for Testing Materials. The No. 50, 30 and 16 sieves are now used in all our 
tests. 

Table 3 — Miscellaneous Tests of Aggregates. 



Test 


Sand 


Pebbles 


Crushed 
Lime- 
stone 


Sand 

and 

Pebbles 


Sand 

and 

Limestone 


Unit Weight of Dry Aggregate 
lb. per cu. ft. 

Absorption of Aggregate * 

Per cent by volume 

Per cent by weight 

Abrasion Test § 

Loss in weight — per cent 


115.5 

2.3 
1.3 


112.5 

2.2 
1.3 

2.3 

8.8 


99.5 

1.6 
1.0 

5.2 
12.3 


131.0 


123.0 










Rea's method 









* After immersion in water at room temperature for 3 hr. 

§Abrasion tests were made in the Deval abrasion testing machine. In the stand- 
ard method a sample of 50 pieces weighing 5000 g. was placed in the test chamber and 
run for 10,000 revolutions. Rea's method was first used by A. S. Rea, of the Ohio 
State Highway Department, Columbus. It consists in using a 5000-g. sample, made up 
of 2500 g. of aggregate J4 to Y$ in. in size and 2500 g. of aggregate 54 to 1^2 in. In 
addition to the aggregate six 1% in. cast-iron balls were placed in the test chamber as 
an abrasive charge. The entire sample was run for 10,000 revolutions. It will be seen 
that Rea's method i% much more severe than the standard method. 

The absorption of the aggregate was determined as follows : 
The sand was dried to constant weight and cooled to room tempera- 
ture in a desiccator. A 500-g. sample was placed in a 500-cc. volumetric 
flask and the volume of water necessary to fill to mark carefully meas- 
ured. At frequent intervals the flask was filled to mark. The zero 
volume was obtained in the same manner, except that the sand was coated 
with kerosene to prevent absorption of water. This is an adaptation of 
Rea's method for determining specific gravity of fine aggregates.** 

*(Note added at Third Printing, September, 1922). This method is now stand- 
ard under the title "Standard Method of Test for Unit Weight of Aggregate for 
Concrete"; Serial Designation C 20-21. 

**See "Apparent Specific Gravity of Non-Homogeneous Fine Aggregates," by A. 
S. Rea. Proc. Am. Soc. Testing Mat., Part II, 1917. 



Structural Materials Research Laboratory 




Fig. 1 — Talbot-Jones Rattler with Concrete Wear Blocks in Place. 

Wear tests were made on blocks 8 in. square, 5 in. thick. 

The coarse aggregate was dried to constant weight, cooled to room 
temperature and weighed, then immersed in water at room temperature. 
At frequent intervals it was removed from the water, quickly surface- 
dried with a towel and weighed. Our experience with these methods 
indicates that the absorption at about 3 hours gives the best results in 
estimating the quantity of water necessary for concrete mixes. 




Fig. 2 — Talbot-Jones Rattler with Head Closed Ready for Test. 

The machine was operated for 18G0 revolutions at 30 r. p. m. 
The abrasive charge consisted of 200 lb. of cast-iron balls. 



Effect of Curing Condition of Concrete 5 

Proportioning and Mixing Concrete. 

In all the tests included in this report the concrete consisted of a 
1 : 4 mix by volume ; that is, 1 volume of cement to 4 volumes of aggre- 
gate mixed as used considering 94 lbs. of cement as 1 cu. ft. This mix is 
equivalent to the 1 : 1^> : 3 or 1:2:3 mixes generally used for one-course 
concrete road construction. The exact equivalent of our 1 : 4 mix when 
expressed in the customary manner will depend on the size and grading of 
the aggregate. 

The concrete was mixed by hand in the manner regularly followed 
in making such tests in this Laboratory. Each specimen was made from 
a separate batch of about Y& cu. ft., which was proportioned separately 



€0OO 




a? 



A00 4/0 /.PO tfO /.SO 432 



Fig. 3 — Effect of Quantity of Mixing Water on the Strength of 

Concrete. 



Compression tests of 6 by 12-in. cylinders at age of 4 months. 
Each value is the average of four tests made on two different 
days. Same data as in Fig. 5. 

and mixed with a bricklayer's trowel in a shallow metal pan. This method 
leaves no uncertainty as to the exact quantities of materials in each specimen. 
The term "consistency" as used in this report refers to the plasticity 
of the concrete; that is, the relative and not the actual quantity of mixing 
water. It has been found convenient to express the quantity of water 
used in the concrete in terms of the volume of cement. This so-called 
water-ratio has been shown to be the best criterion of the strength of 
the concrete. 



6 Structural Materials Research Laboratory 

The consistency which we have called "normal" (relative consistency 
— 1.00) is of such a plasticity that a 6 by 12-in. cylinder* of 1 :4 concrete 
will "slump" y 2 to 1 in. upon removal of the metal form by a steady, up- 
ward pull immediately after molding the specimen. Concrete of relative con- 
sistency of 1.10 will show a slump of 5 to 6 in.; 1.25, a slump of 8 to 9 in. 

Test Pieces. 



This report covers compression tests of 6 by 12-in. concrete cylinders 
and wear tests on concrete blocks 8 in. square and 5 in. in thickness. 

The 6 by 12-in. cylinders were molded in metal forms made of 12-in. 
lengths of 6-in. inside diameter cold drawn steel tubing, which had been 
split along one element by means of a thin slotter. The form was closed 
by a circumferential band. Each form stood on a machined, cast-iron 




.SO /.OO /.SO 2.00 2SO 3.00T S.SO 

Wafer- Ratio to Vo/ume of Cement $f* x 

Fig. A — Effect of Quantity of Mixing Water on the Strength of 

Concrete. 

Compression tests of 6 by 12-in. cylinders at age of 28 days. 
Each value is the average from five tests. Details of these tests 
are not given in this report. 

base plate. A thin sheet of paraffined tissue paper was placed between 
the base plate and the cylinder form. 

In molding the cylinder the form was filled about one-third full and 
the concrete puddled with a Y^-'m. steel bar about 21 in. long. Filling 
and puddling were continued until the form was full. The top was 

*(Note added at Third Printing, September, 1922). Present practice in making 
the slump test for consistency or workability of concrete requires the use of a 4 by 8 
by 12-in. truncated cone. For concrete of a given consistency the cone gives slumps 
about 1/3 less than the cylinder. The truncated cone is specified in the Progress 
Report of the Joint Committee on Standard Specifications for Concrete and Rein- 
forced Concrete and is used in the Tentative Specifications for Workability of Con- 
crete for Concrete Pavements of the American Society for Testing Materials. 



Effect of Curing Condition of Concrete 



Table 4 — Wear and Compression Tests of Concrete. 

Hand-mixed concrete. 1 : 4 by volume. 
Aggregate graded 0-1 % in. 

The same sand used in all tests. 

Coarse aggregate consisted of pebbles or crushed limestone of the same grading. 
The specimens were stored for the period shown in damp sand, the remainder of 
the time in the air of the Laboratory. Age at test, 4 months. 

Wear tests made in Talbot-Jones rattler — total of 1800 revolutions. 

Wear tests are average of five 8 by 8 by 5-in. blocks. 

Compression tests are average of two 6 by 12-in. cylinders. 

The second set of tests in each group was made 2 to 4 weeks after the first. 





Mixing 
Water 


Depth'of Wear — Inches 
8 by 8 by 5-in. Blocks 


Compressive Strength 

lb. per sq. in. 
(6 by 12-in. Cylinders) 


Coarse Aggregate 


>> 
o 
a 

<D O 


o3 


a 

03 

CO a, 

a£ 

c8 O 


.ss 

0,02 


a 

o?a 


M 

o3 
U 

o 


el 

03 

co 

a 2 

So 


-§a 

o3 


ft 

TJ 03 


60 

03 

a 

< 


Pebbles 


.90 
.90 


.66 
.66 


.53 
.54 


.34 
.51 


.82 
.84 


1.29 
.91 


4970 
4990 


5310 
5150 


2890 
2720 


2110 




2260 




.54 

.48 
.52 


.43 


.83 


1.10 


4980 

5970 
5700 


5230 


2810 


2190 


















.50 








5890 








Pebbles 


1.00 
1.00 


.73 
.73 


.54 
.52 


.52 

.41 


.83 

.78 


1.01 
1.10 


5530 
4760 


4550 
4960 


3040 
2960 


2290 




2020 


Crushed Limestone 


.53 

.34 
.46 


.47 


.81 


1.06 


5200 

5800 
5280 


4760 


3000 


2160 


















.40 








5540 








Pebbles 


1.10 
1.10 


.81 
.81 


.52 
.56 


.51 

.54 


1.00 
.98 


1.23 
1.02 


4470 
5020 


3940 
4220 


2350 
2410 


2240 




2050 


Crushed Limestone 


.54 

.48 
.52 


.53 


.99 


1.12 


4750 

5390 
5540 


4080 


2380 


2150 


















.50 








5470 








Pebbles 


1.25 
1.25 


.91 
.91 


.57 
.63 


.51 

.56 


.96 
1.25 


1.56 
1.64 


4700 
4490 


4350 
3640 


2360 
1900 


1640 




1710 


Crushed Limestone 


.60 

.58 
.56 


.54 


1.10 


1.60 


4600 

4320 
4850 


4000 


2130 


1680 


















.57 








4590 








Pebbles 


1.35 
1.35 


.99 

.99 


.59 
.66 


.69 
.69 


1.49 
1.61 


2.40 

1.51* 

1.51 


3860 
3650 


2570 
3190 


1400 
1310 


1420 




1250 




.63 

.59 
.61 


.69 


1.55 


3760 

3910 
3820 


2880 


1360 


1340 


Crushed Limestone 


1.51* 




















.60 








3870 








Pebbles 


1.50 
1.50 


1.09 
1.09 


.74 
• 73 


.85 
.92 


2.34 
2.00* 


1.68 


3740 
3530 


2300 
2440 


1330 
1090 


1280 




1240 




.73 

.60 

.68 


.89 


1.68 


3640 

2640 
3190 


2370 


1210 


1260 


Crushed Limestone 


2.00* 




















.64 








2920 









* Omitting one badly damaged block. 

t One block disintegrated, allowing entire charge to fall out after about 1100 
revolutions. 



Structural Materials Research Laboratory 



6&00 



sooo 



4000 



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9& A'<s'/&/'/i/ie 


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O ?0 40 60 &0 ZOO /<?0 

Fig. 5 — Effect of Curing Conditions on the Strength of Concrete. 

Compression tests of 6 by 12-in. cylinders at age of 4 months. 
Each value is the average of four tests made on two different 
days. Same data as in Fig. 3. 



^7 




.90 



J0O //& s&G SJ0 *?0 JJO 



Fig. 6 — Effect of Quantity of Mixing Water on the Wear of Concrete. 

Wear tests of 8 by 8 by 5-in. blocks at age of 4 months. Each 
value is the average of 10 blocks made on two different days. 
Same data as in Fig. 7. 



Effect of Curing Condition of Concrete 9 

leveled off with a bricklayer's trowel. About 3 to 4 hours after molding, 
a thin layer of neat cement paste (which was mixed at the same time or 
before the concrete) was spread over the top of the cylinder. A piece of 
plate glass and a sheet of paraffined paper were used to form a cap, which 
made a smooth, square end for loading. The glass remained in place 
until the form was removed. 

This method of capping is much better than setting the specimens in 
plaster of paris or a cement-plaster mixture immediately before testing. 
It* has the following advantages : 

(1) The cap is just as strong and stiff as the concrete and forms 

an integral part of the specimen. 

(2) The time and labor required is a small part of that necessary 

with the plaster method. 

(3) The plate glass prevents evaporation of water during the period 

the concrete is in the form. 

(4) The cylinder is ready for test at any time without further prep- 

aration. I 



aoto 




Oft? <?0 60 SO /OC /ft? 

Fig. 7 — Effect of Curing Conditions on the Wear of Concrete. 

Wear tests of 8 by 8" by 5-in. blocks at age of 4 months. Each 
value is the average of 10 blocks made on two different days. 
Same data as in Fig. 6. 

The metal forms for the wear blocks were made. in gangs of three. 
The form was set on a sheet of building paper laid directly on the con- 
crete floor. The form was filled before puddling. The top was leveled 
off with a trowel. After a period of 1 to 2 hours the top of the blocks 
was finished by hand with a wood float. Instead of capping, the blocks 
were covered with a sheet of wet building paper and about 3 in. of damp 
sand. This method prevented loss of water while the blocks were in the 
forms. 



10 



Structural Materials Research Laboratory 



All test pieces were allowed to remain in the metal forms over night. 
Upon removal of the forms they were stored in the manner indicated in 
Table 4. Two cylinders and five wear blocks were made in each group 
before the duplicate sets were begun. The duplicate sets were made two 
to four weeks after the first. 

Methods of Testing. 

The compression tests of concrete were made in a 200,000-lb. Olsen 
universal testing machine. A spherical bearing block was used on top of 
the cylinders. 

Wear tests of concrete were made in the Talbot-Jones rattler. The 
test pieces consist of blocks 8 in. square and 5 in. in thickness. The blocks 
are arranged around the perimeter of the drum of the rattler, as shown in 
Fig. 1. Ten blocks constitute a test set. The ten-side polygon formed by 
the test blocks presents a nearly continuous surface. The outside diam- 



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.&0 70 .SO &0 /.OO /./O 

Fig. 8 — Effect of Quantity of Mixing Water on the Strength and 
Wear of Concrete. 

Average curves from Fig. 3 and 6. The quantity of mixing 
water is expressed as a ratio to the volume of cement in the 
batch. Each value for compression is the average of 20 tests 
(four curing conditions). Each value for wear is the average of 
50 tests (four curing conditions). In interpreting this diagram 
it should be borne in mind that we have averaged the four stor- 
age conditions described in Table 4. For best curing conditions 
the concrete will show a higher strength and much less wear than 
any indicated on this diagram. 



eter of the polygon thus formed is 36 in. and the inside diameter 26 in. 
During the test the front of the chamber is closed by means of a light 
steel plate. The abrasive charge consists of 200 pounds of cast-iron balls 



■ 



Effect of Curing Condition of Concrete 



11 



(about 133 V/ 8 in. and 10 33/ 4 in. in diameter). These balls conform to 
the requirements for the standard rattler test of paving brick of the 
American Society for Testing Materials. 

The test consists of exposing the inner faces of the concrete blocks to 
the wearing action of the charge for 1800 revolutions at the rate of 30 
r.p.m. The machine was run for 900 revolutions in one direction, then 
reversed. Two sets of blocks are tested at once in the machine now in 
use. Each block was weighed upon removal from the form, upon removal 
from the damp sand, immediately before and after testing. The loss in 
weight during the test, reduced to an equivalent depth of wear in inches, 
was used as a measure of the wear. 

Absorption tests were made on two wear blocks from each set of 10. 
The tests were made when the blocks were about one year old, after hav- 
ing been stored in the open air in the laboratory during the period follow- 
ing the wear test. The blocks were dried to approximately constant weight 



6000 



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75 



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Cc?/7cnr/e' S/<an?&'/>7 SJotrT^yO So/yc/} c/&y>S 



Fig. 9— Effect of Curing Condition on the Strength and Wear of 

Concrete. 

, Average curves from Fig. 5 and 7. Each value for compres- 
sion is the average of 24 tests (four each for six consistencies). 
Each value for wear is the average of 60 blocks (10 each for six 
consistencies). The upward trend of the wear curve results from 
the abnormal wear of the 4-month sand-stored blocks on account 
of being tested in damp condition. 

on a steam radiator, weighed and immersed in water at room temperature. 
At various intervals they were removed from the water, allowed to drain 
for about 5 minutes and weighed. The gain in weight was reduced to an 
equivalent volume of absorbed water. 



12 



Structural Materials Research Laboratory 



Discussion of Tests. 

The tests included in this report consisted of compression tests of 
120 6 by 12-in. concrete cylinders and 300 wear tests of 8 by 8 by 5-in. 
blocks, as well as miscellaneous tests of cement and aggregate. A 1 : 4 
mix was used throughout, with aggregate graded up to l^.-in. In general 
the coarse aggregate was pebbles ; in one group of tests crushed limestone 
was used. This mix is approximately the same as that generally used in 
one-course concrete road construction. Four different curing conditions 
were used for pebble aggregate as follows : 

(1) Damp sand 4 months, tested damp, . 

(2) Damp sand 21 days, air 99 days, 

(3) Damp sand 3 days, air 117 days. 

(4) Air of laboratory for entire curing period of 4 months. 



7000 



sooo 



X 



\ 40OO 

X 

^ JOOO 

I 



/OOO 









Mix /-A 










• 




/ 


^ea 


//** 


+ 4rr, 


o. 








D 












'es 
tone 






\ ° 


















• O ^ 


^V 


i 
























> 


•^ • 




















7S 



.e /.O /.? £4 A6 

Wear — /'nc/ies 



e.o 2,2 



Fig. 10 — Relation Between the Strength and Wear of Concrete. 

Compression tests of 6 bv 12-in. cylinders, and wear tests of 
8 by 8 by 5-in. blocks at age of 4 months. Each value is based 
on the averages of four compression tests and 10 wear tests. 
All consistencies and curing conditions are included. 



Group (1) was repeated, using crushed limestone as coarse aggregate. 
All compression and wear tests were made at age of 4 months. Average 
values from the strength and wear tests are given in Table 4. 



Effect of Curing Condition of Concrete 



13 



Effect of Quantity of Mixing Water on the Strength of Concrete. 

Fig. 3 gives the results of the tests on the effect of quantity of mixing 
water on the compressive strength of concrete. A separate curve has 
been drawn for each curing condition. An average curve from these tests 
will be found in Fig. 8. The remarkable influence of the quantity of 
mixing water on the strength, other factors being the same, is clearly 
shown by these curves. It will be remembered that the consistency which 
we have called 1.00 (normal consistency) is such that a 1 : 4 mix gives a 
slump of ^ to 1 in. when the form is slipped off the freshly molded 
cylinder. A consistency of .90 contains 90 per cent of the amount of 
water required for normal consistency; a consistency of 1.50 contains 



eooo 

ssoo 

» sooo 

\ 4SOO 
^ 4000 



i 

r 



eooo 

































































A 


//> /-4 






















/?g<s 


>eff 


1 
?sf 4/na 


















































































\ 




*, 


























^ 












































7S 

r/'8 





























.6 .7 .<? 

Wear- /nc/ies 



/& AC 40 2f> 



sc<?M = A' 



Fig. 11 — Relation Between Strength and Wear of Concrete. 

Same data as in Fig. 10, except curve platted on logarithmic 
scales. The points shown are taken from the curve in Fig. 10. 

\ x / 2 times the quantity of water used in the normal consistency concrete, 
etc. The normal consistency concrete may be characterized as plastic; 
the .90 is somewhat dry; the 1.50 quite wet, but contains much less water 
than the "sloppy" mixes frequently seen in reinforced concrete work. 

It will be noted that there is a rapid falling-off in strength as the 
water content is increased from normal consistency. With a consistency 
of 1.25 the strength is reduced to about 75 per cent of the highest; with 
a consistency of 1.50 the strength is only one-half that which may be 



14 



Structural Materials Research Laboratory 



obtained with the same cement content. For wetter mixes the strength 
would be still further reduced. 

In general it is not feasible to use concrete of a consistency 
which will give maximum strength, since it is somewhat too stiff for satis- 
factory workability. In concrete road work where hand finishing is used 
the concrete must be mixed to a consistency varying from 1.10 to 1.15. 
In other words, we must sacrifice a portion of the possible strength of 
the concrete in order to secure a workable mix. This consistency will 
give a slump of 5 to 7 in. If machine finishing is employed, the concrete 




.70 #Z? //O 4&D 4JO 4?0 {5& 

Fig. 12— Effect of Quantity of Mixing Water on the Absorption of 

Concrete. 

Absorption tests of 8 by 8 by 5-in. blocks. Pebble aggregate. 
Age 1 year. Absorption determined after immersion in water at 
room temperature. Each value is the average of eight blocks 
from four different curing conditions — one block from each set 
of pebble aggregates in Table 5. Absorption is given by volumes; 
absorption by weight is about 40 per cent of these values. 

can be mixed to a consistency corresponding closely to maximum strength. 
In reinforced concrete work there is in general little excuse for using 
mixes wetter than 1.25 consistency, corresponding to a slump of 8 to 9 in. 
The average curves in Fig. 8 have been platted in terms of the water- 
ratio instead of the relative consistencies, although relative consistencies 
are also shown. The water-ratio is the ratio by volume of water to cement 
in the batch. 



Effect of Curing Condition of Concrete 



15 



Further Discussion of Effect of Quantity of Mixing Water on the 
Strength of Concrete. 

Many series of tests made in this Laboratory have fully established 
the fundamental influence of the quantity of mixing water on the strength 
of concrete. 

Fig. 4 gives the average values from a series of tests of this kind 
in which the compressive strength is platted against the water-ratio of 
the concrete. In this series the mixes ranged from 1 : 15 up to neat cement. 
The consistencies were varied over a wide range. The size of the aggre- 



/s 



/? 



y 


// 


1 


/0 


s 


? 


* 


# 


> 




fc 




y 


7 


V 




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6 


x 


s 

S 
P 


% 



















































AN 




























^ 


^ 
















l\ 






22. 


2^ 


r-rt 


?<* 


077S2 


7C-SIS 


So/7 


V 
















7& 




, 




. f &c 






\ 


v ^ 












^7sf~ 


g^v 









\ 














^T7 










|* f 






















. \ 
S/?sz 




































At 


%-/ 


46) 


* fa 


4//?-, 


£> 

























































/ 



O PO 40 60 <50 /00 /P0 

Fig. 13 — Effect of Curing Conditions on the Absorption of Concrete. 

Absorption tests of 8 by 8 by S-in. blocks. Absorption deter- 
mined after immersion in water at room temperature. Each 
value is the average of 12 blocks from six different consistencies. 
Same data as in Fig. 12. Absorption is given by volumes; ab- 
sorption by weight is about 40 per cent of these values. 

gate ranged from a very fine sand to a coarse concrete aggregate, for all 
combinations of mix and consistency. Further details of these tests are 
not given in this report. 

In the figure distinguishing marks were used for each mix, but no 
distinction was made between aggregates of different sizes or concretes 
of different consistencies. When the compressive strength is platted 
against the water content in this way a smooth curve is obtained due to 



16 



Structural Materials Research Laboratory 



the overlapping of the points for different mixes, consistencies, etc. Val- 
ues from the dry concretes have been omitted from the diagram; if these 
were used we should obtain a series of curves dropping downward to 
the left from the curve shown. It is seen at once that the size and grading 
of the aggregate and the quantity of cement are no longer of any impor- 
tance, except in so far as these factors influence the quantity of mixing 
water required to produce a workable concrete. This gives an entirely 
new conception of the function of the constituent materials entering into 
a concrete mixture. 

The equation of the curve in Fig. 4 is of the form 

A 

B* 

where .S is the compressive strength of the concrete and x (an exponent) 
is the ratio of the volume of water to volume of cement in the batch 
(water-ratio). A and B are constants whose values depend on the quality 
of the cement used and on other conditions of the test. 





























-4 


/ 


sr 


-— 


-* 






















/ 


\ 


























I 


\ 




































M 


W/-4 


*3y 


\4>/o 


Tre 




















































































































































Sri 






s 




















\ 



/OO 200 JOO 4<X? SOO 

ZV77£> Of*J?77/77&rSy0S7-S7C>t/S-S 



Fig. 14 — Effect of Time of Immersion on the Absorption of Concrete. 

Absorption tests of 8 by 8 by 5-in. blocks. Absorption deter- 
mined after immersion in water at room temperature. Each 
value is the average of 48 tests from six consistencies and four 
curing conditions. Data from Table 5. Absorption is given by 
volumes; absorption by weight is about 40 per cent of the these 
values. 



The values of the constants in these tests are shown on the diagram. 
This equation expresses the law of the strength of concrete so far as 
variations in the proportions of materials are concerned. It is seen that 
for given concrete materials the strength depends on only one factor — 
the water-ratio. Equations which have been proposed for this purpose 
in the past contain terms which take into account such factors as quan- 



Effect of Curing Condition of Concrete 



17 



Table 5 — Absorption Tests of Concrete. 

Mix 1:4 by volume. Hand-mixed concrete. 

Aggregate graded 0-1 34 in. 

The same sand used in all tests — torpedo sand from Elgin, 111. 

Coarse aggregate consisted of pebbles or crushed limestone of same grading. 

Age at test 1 year. The tests were made on 8 by 8 by 5-in. concrete blocks which 
had previously been used in wear tests at the age of 4 months. Immediately after 
molding the blocks were stored for the period shown in damp sand, the remainder 
of the time in the air of the Laboratory. 

During the absorption test the blocks were immersed in water at room temperature. 

Each value is the average of 2 blocks made on different days. 





Mixing 
Water 


Absorption — Per Cent by Volume 


Coarse 
Aggregate 


>> 
a 

•■-".2 
J a 

9 O 


.9 

S 

o3 


9 

02 to 

?? 


.as 

0qO2 

-d S 


T3 

a 
a °3 

•-02 

It 


ID 
| 
1 

02 
< 


a 

o3 
02 (o 

a £ 


.SS 

cn02 
03 7* 

-o S 


T3 
fl 

•"02 

It 

T3 o3 




sr 

02 

u 

< 


d 

03 
02 © 

»o? 

J S 

Q02 


73 

•S 03 
en 02 

£& 

T3 a 


13 

O 

fl 03 

•"02 

eoQ 


bd 
03 

Ih 
O 

02 
M 
< 






.66 

.66 
.73 
.73 
.81 
.81 
.91 
.91 
.99 
.99 
1.09 
1.09 


3 Hours 


6 Hours 


24 Hours 


Pebbles 


.90 
.90 
1.00 
1.00 
1.10 
1.10 
1.25 
1.25 
1.35 
1.35 
1.50 
1.50 


3.17 

4.66 
4.47 
2.53 
2.58 
2.89 
5.56 
4.30 
4.58 
4.72 
4.58 
5.07 


3.93 


6.41 


8.09 


3.81 
5.15 
5.05 
3.47 
4.77 
4.16 
5.48 
5.27 
5.97 
6.23 
6.56 
5.52 


4.49 


7.70 


9.53 


4.99 
6.52 
6.11 
4.71 
5.11 
4.75 
5.99 
6.02 
7.21 
7.40 
7.18 
8.44 


6.26 


8.84 


11.00 


Pebbles 


4.00 


6.71 


7.32 


4.50 


7.96 


8.74 


6.05 


9.59 


9.61 


Pebbles 


5.07 


8.18 


10.30 


6.06 


9.58 


10.66 


8.00 


10.60 


11.80 


Pebbles 


4.23 


8.52 


10.20 


5.82 


9.91 


11.40 


7.67 


10.60 


12.10 


Pebbles 


6.25 


11.90 


10.70 


7.63 
'7.85 


12.81 

ii.92 


11.61 
13.65 


9.86 
l6'.90 


13.60 
13.50 


11.90 


Pebbles 


6.36 


9.11 


11.60 


14.30 




























48 Hours 


3 Days 


7 Days 


Pebbles 

Cr. Limestone. 
Pebbles 


.90 

.90 
1.00 
1.00 
1.10 
1.10 
1.25 
1.25 
1.35 
1.35 
1.50 
1.50 


.66 

.66 
.73 
.73 
.81 
.81 
.91 
.91 
.99 
.99 
1.09 
1.09 

.66 
.66 
.73 
.73 
.81 
.81 
.91 
.91 
.99 
.99 
1.09 
1.09 


5.08 
6.74 
6.20 
4.85 
5.49 
5.26 
7.30 
6.54 
8.05 
7.91 
8.02 
8.82 


6.76 
' 7.06 


9.06 

16.66 


11.36 
' 9'.89 


6.08 
6.03 
6.54 
5 56 


7.06 
*7l72 
"8.70 
' 9.22 
i6'.42 

ii.45 


9.35 

i6'.58 
i6.74 
13.05 
14.75 
13.65 


11.75 
i6.53 
i2'.35 
l2'.30 
13.22 
i4.86 


6.46 
6.98 
7.24 
5.76 
6.76 
6.90 
7.42 
8.06 
8.98 
8.85 
9.92 
9.10 


7.31 
7!55 
' 9.72 
'9.14 


9.44 
i6.34 

ii.45 

i3.50 


11.16 

io'io 


Pebbles 

Cr. Limestone. 
Pebbles 


9.26 
" 7.94 

io'.ii 

i6.95 


9.98 

ii'io 

14.20 

i3'.50 


11.85 

12.66 

12.30 
14.45 


6.88 
6.20 
7.65 
7.08 
8.94 
8.35 
8.49 
9.16 


10.95 

ii'.so 


Pebbles 

Cr. Limestone. 
Pebbles 


10.21 
10.81 


14.40 
12.92 


12.97 
i4.32 


























28 Days 




Pebbles.. 


.90 
.90 
1.00 
1.00 
1.10 
1.10 
1.25 
1.25 
1.35 
1.35 
1.50 
1.50 


9.07 
7.54 
5.68 
5.92 
7.00 
5.64 
7.88 
8.30 
9.13 
9.43 
10.15 
9.23 


7.82 


9.63 


12.22 




Pebbles 


7.84 


10.92 


10.25 




Pebbles 


9.43 


11.68 


11.27 




Pebbles 


9.84 


14.25 


13.18 




Pebbles 


10.74 


15.08 


14.19 




Pebbles 


11.72 


15.40 


16.50 





























18 



Structural Materials Research Laboratory 



tity of cement, proportions of fine and coarse aggregate, voids in aggre- 
gate, etc., but they have uniformly omitted the item which is of most 
importance; that is, the water. The relation given above holds so 
long as the concrete is not too dry for maximum strength, and the aggre- 
gate not too coarse for a given quantity of cement; in other words, so 
long as we have a workable concrete. 

The strength of the concrete responds to changes in water, regard- 
less of the reason for these changes. The water-ratio may be changed 
due to any of the following causes : 

(1) Change in mix (cement content). 

(2) Change in size or grading of aggregate. 

(3) Change in relative consistency. 

(4) Any combination of (1) to (3). 

Table 6 — Unit Weight of Concrete. 

Mix 1:4 by volume. Hand-mixed concrete. 
Weighed immediately before test at age of 4 months. 
Aggregate graded 0-1 J4 in. 

The same sand used in all tests. 

Coarse aggregate consisted of pebbles or crushed limestone of same grading. 
The tests were made on 8 by 8 by S-in. blocks and 6 by 12-in. cylinders. 
Test pieces were stored for the period shown in damp sand, the remainder of the 
time in the air of the Laboratory. 

Each value is the average of 4 cylinders and 10 wear blocks. 





Mixing Water 




Weight— 1 


b. per cu. ft. 




Aggregate 


Relative 

Consistency 


Water 
Eatio 


Damp Sand 
Storage 


21 da. in 
Damp Sand 


3 da. in 
Damp Sand 


Air 
Storage 


Pebbles 


.90 
.90 

1.00 
1.00 

1.10 
1.10 

1.25 
1.25 

1.35 
1.35 

1.59 
1.50 


.66 
.66 

.73 
.73 

.81 

.81 

.91 
.91 

.99 
.99 

1.09 
1.09 


155.8 
152.5 

157.0 
152.0 

156.9 
156.0 

155.9 
156.2 

156.9 
155.6 

154.8 
156.0 


148.5 


147.0 


147.0 






Pebbles 


153.0 


152.0 


151.0 






Pebbles 


152.0 


150.5 


149.8 






Pebbles.: 


152.0 


148.5 


148.0 






Pebbles 


152.0 


149.8 


150.2 






Pebbles 


149.5 


148.2 


148.0 















In certain instances a 1 : 9 mix is as strong as a 1:2 mix, depending 
only on water content. It should not be concluded that these tests indi- 
cate that lean mixes can be substituted for richer ones without limit. 
We are always limited by the necessity of using sufficient water to secure 
a workable mix. So in the case of the grading of aggregates. The work- 
ability of the mix will in all cases dictate the minimum quantity of water 
that can be used. The importance of the workability factor in concrete 
is therefore brought out in its true relation. 



Effect of Curing Condition of Concrete 



19 



Designing concrete mixes resolves itself into the problem of 
producing a workable concrete with a given water-ratio using a mini- 
mum of cement; or the converse, of producing a workable concrete 
which has the lowest water-ratio for a given quantity of cement. The 
methods of securing the best grading of aggregate and the use of the 
driest practicable concrete are seen to be only devices for accomplishing 
the above-mentioned results. A forthcoming Bulletin on the "Design of 
Concrete Mixtures"* will give further details of the principles underlying 
the proportioning of concrete, and discuss their application to practical 
problems. 

The influence of the water-ratio of concrete on its strength will be 
shown by the following considerations : One pint more water than neces- 
sary to produce a plastic concrete in a 1:4 mix reduces the strength to 
the same extent as if we should omit 2 to 3 pounds of cement from a 
one-bag batch. 




Fig. 15 — Front View of Wear Blocks After Test. 

Top row, gravel as coarse aggregate. 

Bottom row, crushed limestone as coarse aggregate. 

Our studies give us an entirely new conception of the function per- 
formed by the various constituent materials. The use of a coarse, well- 
graded aggregate results in no gain in strength unless we take advantage 
of the fact that the amount of water necessary to produce a plastic mix 
can thus be reduced. In a .similar way we may say that the use of more 
cement in a batch does not produce any beneficial effect, except from the 
fact that a plastic, workable mix can be produced with relatively less 
water. 

The reason a rich mixture gives a higher strength than a lean one 
is not that more cement is used, but because the concrete can be mixed 
(and usually is mixed) with a lower water-ratio in the case of the richer 
mixtures than for the lean ones. If advantage is not taken of the fact 



* See Bulletin 1, Structural Materials Research Laboratory. 



20 



Structural Materials Research Laboratory 



that in a rich mix relatively less water can be used, no benefit will be 
gained as compared with a leaner mix. In all this discussion the quan- 
tity of water is compared with the quantity of cement in the batch (cubic 
feet of water to one sack of cement) and not to the weight of dry ma- 
terials or of the concrete, as is generally done. 

For the other curves showing the strength water-ratio relation, see 
paper on "Time of Mixing Concrete," referred to on page 1. 

Effect of Quantity of Mixing Water on the Wear of Concrete. 

Fig. 6 and 8 give the results of tests to determine the effect of 
quantity of mixing water on the wear of concrete. It will be noted that 
the depth of wear is expressed in inches. The wear-water-ratio relation 




Fig. 16 — Side View of Concrete Blocks After Wear Test. 



is just opposite to that found in the strength tests ; in other words, a 
high strength is accompanied by low wear, and vice versa. If the wear 
curve in Fig. 8 were inverted we should have almost a duplicate of the 
strength curve. In general, the lowest wear is found at about the same 
water-ratio as the highest strength. The average curves (Fig. 8) show 
that maximum strength and minimum wear come at a consistency of 
about .95, or a water-ratio of about .70. It should be pointed out that 
for other mixes the best results would probably be found at about the 
same relative consistency, but at a different water-ratio. For a given 
consistency the water-ratio is higher for lean mixes and lower for xich 
mixes. . . : . . . : 



Effect of Curing Condition of Concrete 



21 



The relation between the depth of wear and the water-ratio of the 
concrete for blocks stored for 21 days in damp sand is expressed by the 
equation 

W = 0.15 (4.8"). 

Where W is the depth of wear expressed in inches, and x (an expo- 
nent) is the water-ratio. A similar relation was found in the series of 
wear tests in the paper on "Time of Mixing Concrete," referred to above. 



Water Required for Concrete. 

Since the quantity of mixing water exerts such an important influence 
on the strength and other properties of concrete, it will be of interest 
to examine the factors which influence the amount of water required for 
satisfactory results. The function of water in concrete is twofold: 

(1) To supply the water necessary for hydration of the cement, 

(2) To produce a plastic mixture. 

While the exact quantity of water required under (1) has not been 
determined except .in certain instances, it is generally agreed that the 
quantity used in concrete is greatly in excess of that necessary for hydra- 
tion of the cement. The bulk of the water in concrete is used in order 
to produce a plastic or workable mix. The exact quantity required for 
this purpose depends on the materials used, nature of the work, and 
methods of handling and finishing. 

It is, in general, impracticable to state definitely the quantity of water 
which should be used, since this depends on many factors, such as : 

(1) Relative consistency which must be used, which is dictated by 

the nature of the work, 

(2) Normal consistency of.the cement, 

(3) Quantity of cement, 

(4) Size and grading of the aggregate, 

(5) Absorption of the aggregate, 

(6) Moisture content of the aggregate, 

(7) Admixtures which may be used. 

A water formula has been developed which takes into account all 
these elements ; for further details see Bulletin 1, "Design of Concrete 
Mixtures." 

The quantity of water which affects the water-ratio as given in Fig. 8 
is only such a part of the whole as affects the cement. In other words, 
the water which is absorbed by the aggregate is not considered as in- 
fluencing the water-ratio. This makes it plain that the absorption of the 
aggregate must be taken into account if concretes from widely different 
aggregates are being compared. Many serious errors have been made in 
drawing conclusions from tests, due to failure to take into account the 
influence of absorption, grading of aggregates, etc., on the water content 
of the concrete. 



22 



Structural Materials Research Laboratory 



CONSISTENCY 




Sanh U s 



SaS6 4»« 


B 1 


Sas«4mq 

C8- STOKE 


1.1 ( 



Fig. 17 — Side View of Wear Blocks After Test. 

The effect of curing condition on wear is clearly shown. 



I 



CONSISTENCY I 

■rum: t 




Fig. 18 — Side View of Wear Blocks After Test. 

The effect of curing condition on wear is clearly shown. 



Effect of Curing Condition of Concrete 



23 



In general, it is impracticable to determine in advance the exact 
quantity of water required for concrete mixes, largely due to two causes : 
(1) Inability to determine in advance the lowest relative consistency 
which may be used and still produce a workable concrete ; (2) varying 
moisture content of aggregates. 

Table 7 may be of interest in indicating the approximate quantities 
of water necessary for certain mixtures. It is assumed that a well-graded 
aggregate up to \y 2 in. in size will be used. Only under the most favorable 
conditions can the minimum values be used ; in general, the minimum 
values need not be exceeded. 

Table 7 — Quantity of Water Required for Mixing Concrete. 



Mix 


Approximate Mix as Usually- 
Expressed 


Water Required 
(Gallons per Sack 
of Cement) 


Cement 


Volume of 

Aggregate 

After Mixing 


Cement 


Aggregate 


Minimum 


Maximum 




Fine 


Coarse 




1 
1 
1 
1 

1 

1 


7% 

5 

4 
3 




3 

23^ 
2 
2 
IK 

IK 


6 
5 
4 
3 
3 
2H 


8M 
6 

5A 
5 


8M 
7M 
6K 

GH 

6 

5A 



Without regard to the actual quantity of mixing water, the following 
rule is a safe one to follow: 

"Use the smallest quantity of mixing water that will 
produce a workable mix." 

The importance of methods of proportioning, mixing, handling, plac- 
ing or finishing concrete which will enable the builder to reduce the water 
content to a minimum is at once apparent. 



Effect of Curing Condition on the Strength of Concrete. 

The effect of curing condition on the compressive strength of con- 
crete is shown in Fig. 5 ; an average curve is given in Fig. 9. All con- 
sistencies of concrete show great increases in strength under favorable 
curing conditions as compared with specimens which were allowed to 
dry out at once. The drier mixes show a more rapid improvement due 
to storage in a damp place during the first few days than the wetter 
ones. Even 3 days in damp sand shows an increase in strength of the 
drier concretes of about 35 per cent as compared with the specimens 
stored in open air for the entire period. It should be borne in mind that 
in the most unfavorable case used in the experiments the concrete was in 
the steel form for 1 day with only the top exposed, consequently the con- 
ditions were more favorable than those frequently found in summer 
weather or in arid regions where the concrete is exposed to rapid evapora- 
tion of the mixing water from the moment it is placed. 



24 



Structural Materials Research Laboratory 




>. -;. 



& CONSISTENCY 

LLLLtlll 

I 

Lit 




SAS6 4? 



SSSB4M9 




Fig. 19 — Side View of Wear Blocks After Test. 

The effect of curing condition on wear is clearly shown. 




Fig. 20 — Side View of Wear Blocks After Test. 

The effect of curing condition on wear is clearly shown. 



Effect of Curing Condition of Concrete 



25 



The concrete stored for 4 months in damp sand and tested damp is 
2y 2 to 3 times as strong as similar concrete which has been exposed to 
room atmosphere for the same period. Protecting the concrete from dry- 
ing out for only 10 days (taking values from Fig. 5 and 9) gives an 
increase in strength of about 75 per cent for the drier consistencies. 

Effect of Curing Condition on the Wear of Concrete. 

The effect of curing condition on the wear of concrete is no less strik- 
ing than the effect on the strength. 

It will be seen in Fig. 7 that the blocks stored for the entire period 
of 4 months in damp sand showed more wear in most instances than those 
which had been stored for 21 days in damp sand and the remainder of 
the time in air. This peculiar result is no doubt due to the fact that the 
concrete was tested in a damp condition, and does not indicate that the 
longer period in damp sand is injurious. The comparison would have 
been more nearly correct if the blocks had been allowed to dry out a 
few days before testing. These results do show that concrete in a wet 
or damp condition suffers more from wear than when dry. It is a mat- 
ter of common experience that non-metallic materials, such as timber, 
terra cotta, concrete, stone, etc., which absorb water, show a lower strength 
in a wet condition than when dry. Additional tests will be required to 
show the exact effect of moisture content on strength and wear of con- 
crete, other factors being the same. 

It is not necessary to speculate on the probable effect of moisture in 
the concrete in order to secure valuable information from these tests. 
The drier mixes show an increase in wear from .50 in. for concrete 
stored in damp sand for 21 days to 1.10 in. for concrete in air for* entire 
period ; the tests show that 10 days in damp storage gives a wear 
of about .65 in. For the wetter mixes the wear after 21 days in damp 
sand is about .85 in. ; for 10 days, 1.15 in. ; for air storage throughout, 
probably 2 in. In the wetter consistencies the tests were not carried to 
completion on account of the failure of certain blocks, which caused 
the entire ring to collapse. 

The photographs in Fig. 16 to 21 show side views of the blocks after 
test. The effects of both consistency and curing condition are clearly 
shown by the relative thickness of the blocks. 

Recapitulation of Effect of Consistency and Curing Condition. 

In view of the important influence of consistency and curing condi- 
tions of concrete shown by these tests, it seems doubtful if there is any 
phase of concrete work which will pay such high dividends as a little 
care to see that proper consistency is used and that desirable curing con- 
ditions are provided. In many instances the quality of the concrete could 
be vastly improved at trifling expense; but nothing is done because those in 
charge do not appreciate the importance of care in these directions. The 
writer is convinced that practically all of the faults from concrete floors 
follow from these two causes. Excessive wear and dusting are certain 



26 Structural Materials Research Laboratory 

to result in a floor in which the concrete is never allowed to have the 
water necessary for hydration of the cement. It is notable that dusting 
never occurs on a concrete road, for the reason that it gradually gets the 
water necessary for hydration from rain or snow. However, due to low 
wearing resistance at early periods, resulting from premature drying, it 
may be badly worn before rain comes. 

An excess of mixing water is a serious fault in concrete. If, in addi- 
tion, the concrete is allowed to dry out at once it is almost certain to be 
a failure, if subjected to wear, and will give very low strength. For the 
two wettest consistencies and the two most unfavorable curing conditions, 



Storage 



Sass 2 







Fig. 21 — Side View of Wear Blocks After Test. 

Some of the blocks which were stored for the entire 4 months 
in air were completely broken up before the end of the test run. 
The blocks missing from the two lower rows were lost before the 
photograph was taken. 



the compressive strength of the pebble concrete was 1300 lb. per sq. in. ; 
for the two most favorable curing conditions and the three driest con- 
sistencies the average compressive strength was 4850 lb. per sq. in. — an in- 
crease of 275 per cent. In the case of the wear tests the corresponding 
values are 1.70 in. and .50 in.; an increase of 240 per cent. The com- 
parison in the wear test is not as unfavorable as it should have been, since 
the poorer blocks broke up before the test was completed. 

Proper curing of concrete is second only in importance to the control 
of mixing water. The rule stated above with reference to water content 
may now be extended to the following : 



Effect of Curing Condition of Concrete 



27 



Use the smallest quantity of mixing water that will 
produce a workable concrete, then allow the concrete to 
have as much water as possible during the period of 
curing. 

All concrete should be protected against premature drying for at least 
one week, and longer if practicable. This period should be extended to 
10 days or two weeks in cool weather, or where the concrete is to be 
subjected to heavy traffic at an early age. 

Covering with damp sand or earth, or wet burlap are excellent 
methods of curing. The practice of "ponding" is common in road con- 
struction. The writer wishes to offer a word of caution with reference 
to the use of wet sawdust for covering concrete floors. Sawdust may 
have most harmful results, on account of the organic acids present. 

Compression tests of concrete made in other series show that the 
strength of concrete increases indefinitely, so long as it is not permitted 
to dry out.* 

Relation Between Strength and Wear of Concrete. 

The relation between strength and wear of concrete in this series is 
shown in Fig. 10. All tests have been platted. Each value is based on the 
average of four compression tests and 10 wear tests. This diagram 
shows that a definite relation exists between strength and wear at least for 
the conditions of these tests; that is, for concrete of different consistencies 
and curing conditions. Further tests will be necessary to show whether 
or not this relation is entirely general for other aggregates, etc. 

Fig. 11 is the same curve platted to a logarithmic scale. The straight 
line in this diagram enables us to devise the equation : 

2230 

as showing the relation between the variables ; where S = compressive 
strength in pounds per square inch and W = the depth of wear in inches. 
A similar relation from another series of strength and wear tests 
made in this laboratory will be found in Fig. 14 and 15 of the paper on 
"Effect of Time of Mixing," referred to on page 1. 

In the earlier series of tests the relation between strength and wear 
of concrete was expressed by 

1800 

S = 

W 1 - 30 
The agreement between the equations from the two different series 
of tests is quite close when we consider that the earlier series was tested 
at 2 mo. and the later at 4 mo. 



* See "Effect of Age on the Strength of Concrete," by D. A. Abrams, Proc. 
Am. Soc. Testing Mat., Part II, 1918; also Concrete, July, 1921, p. 14. 



28 



Structural Materials Research Laboratory 



Comparison of Pebble and Crushed Stone Aggregate. 

Crushed limestone was used as coarse aggregate in one group of 
tests. In general the limestone concrete gave somewhat higher strength 
and lower wear than the gravel concrete using the same sand and the 
same water and cement. However, the tests do not cover a sufficient 
range to justify definite comparisons of the merits of the two types of 
aggregate. Both of the aggregates used in this series were of high grade 
and gave good results in the tests. Other tests now under way and 
planned for the future are expected to give definite information on the 
relative merits of different aggregates. 

Method of Making Wear Tests. 



The Talbot-Jones rattler has been found entirely successful as a 
method of studying the wear of concrete in the laboratory. The results 
of the tests thus far completed and the definite relations found between 
the wear and strength have given considerable confidence to this method 
of testing. The abrasive charge of 200 pounds of cast-iron balls, and the 
rate and number of revolutions used, gives a wearing action suited for 
a wide range in the properties of concrete. A very poor concrete may 
be entirely destroyed, a high-grade concrete will show a wear of x / 2 inch 
or less. 

The test gives a combination of abrasion and impact that cannot be 
withstood by an inferior concrete. The severity of the impact may be 
seen from the fact that frequently the 1%-in. cast-iron balls are broken 
during the test. While the test does not fully duplicate the action of 
traffic, it furnishes a valuable guide to the relative effects of different 
methods of treatment, materials, etc., for use in pavement construction. 

This method of making wear tests of concrete is believed to have 
the following advantages as compared with other methods which have 
been used or proposed for this purpose : 

(1) The concrete is subjected to a treatment which ap- 
proximates that of service. 

(2) The test piece is of usual form and of sufficient size 
that representative concrete can be obtained. 

(3) The test pieces are convenient to make, store and handle, 
and require a relatively small quantity of concrete. 

(4) The cost of tests is not excessive. 

(5) The machine used is found in a number of testing lab- 
oratories. 

(6) The wearing action takes place on the top or finished 
surface of the concrete. This makes it possible to study the 
effect of various surface treatments and finishes. 

(7) Several tests may be made at the same time, thus en- 
abling more representative results to be obtained. 



Effect of Curing Condition of Concretk 29 

(8) Tests may be made on sections of concrete cut from 
roads which have been in service. 

(9) Other paving materials, such as brick, granite blocks, 
etc., may be tested in the same manner as the concrete. 

Absorption Tests of Concrete. 

Absorption was determined on two wear blocks from each set of 
1.0, after immersion in water for periods of 3 hours to 28 days. It 
should be noted that absorption tests were made on blocks at the age 
of 1 year, which had been tested for wear at 4 months. 

The results of absorption tests are given in Table 5, and in Fig. 13 
and 14. In Fig. 13 all consistencies for a given curing condition have 
been averaged. It is interesting to note that the absorption is influenced 
by the curing condition of the concrete in the same way as the wear. 
(Compare Fig. 13 and 7.) The curing condition that gives high wear, 
gives high absorption, and vice-versa. 

The effect of consistency and curing condition on absorption is 
shown by an average absorption of 5.77 per cent for the most favorable 
conditions after 24-hour immersion and 12.6 per cent for the most un- 
favorable conditions. The absorption is here given by volumes ; the ab- 
sorption by weight would be only about 40 per cent of these values. 

The effect of time of immersion on the absorption is shown in Fig. 
14; all consistencies and curing conditions have been averaged for a given 
time of immersion. 

Unit Weight of Concrete. 

The unit weight of all test pieces was determined immediately before 
test at the age of 4 months. The values are given in Table 6. Each 
value is the average from four cylinders and 10 wear blocks. The weight 
of the concrete is little affected by the consistency, but is greatly influenced 
by the curing condition. The weights of the specimens stored for 4 
months in damp sand cannot be compared directly with the others, since 
they contained free moisture ; that is, water in the uncombined state. A 
comparison of the average weights of all consistencies for the other curing 
conditions shows that the concrete stored 3 days in damp sand took up 
.33 lb. more water and that^stored for 21 days in damp sand 2.16 lb. more 
water per cubic foot than that stored in air throughout the 4 months. 
Since all test pieces were in the same room-dry condition when the weights 
were determined, it seems that these values may be taken as approxi- 
mate measures of the additional quantities of water which have entered 
into chemical combination with the cement, due to storage in a damp place 
for these periods. 



30 



Structural Materials Research Laboratory 



BIBLIOGRAPHY. 

The following list contains the more important titles to articles having a bearing 
on the subject-matter of this report. Many of the text books on concrete and rein- 
forced concrete give data on the effect of consistency on the strength of concrete. 

Wear Tests of Concrete and other Paving Materials. 



Abrasive Resistance of Paving Materials, by J. Bauschinger; 
Communications, V. 11, 1884. 

Drawing of machine and table of results in Johnson's Materials of Construction, 
4th Ed., p. 650, 1898. 
Tests on 4-in. cubes pressed against revolving iron plate, using emery as abrasive. 

Wearing Qualities of Cement for Paving Purposes, by Gary; 
Jl. Soc. Chem. Ind.. p. 465, 1890. 

Wear and Tear of Roads and the Problem of Meeting Same, by W. J. Taylor; 
Surveyor, Nov. 12, 1908. 

Abrasion Losses of Cement and Cement Mortar, by H. Burchartz; 
Tonind. Ztg.. v. 36, p. 513, 1912. 
Chem. Abs., v. 6, p. 1831. 1912. 

Cubes of neat cement and cement-sand mortars were measured for loss under 

sand blast for 1, 3, and 5 minutes, and after 28 days, 6 months and 1 year. 

Loss was less for richer mixes, older specimens and shorter time of blasting, 

but not comparable. 

A "Pavement Determinator" was on exhibition in Detroit in 1912 and at the Chicago 
Cement Show, 1913. 
Concrete-Cement Age. Dec. 1921. 
Eng. Rec, p. 457, Oct. 25.' 1913. 

Concrete Road Making Properties of Minnesota Stone and Gravel, by Chas. F. Shoop; 
Studies in Engineering No. 2, University of Minnesota, 1915. 

Tests on concrete composed of several different aggregates using annular ring 
specimen in a Talbot- Jones rattler. 

Comparative Tests of Wearing Qualities of Paving Brick and Concrete, by F. L. Roman; 
Municipal Engineering, Aug., 1916. 

Method of Making Wear Tests of Concrete, bv D. A. Abrams; 
Proc. Am. Soc. Testing Mat.. Part II. 1916. 

First description of wear tests of separately molded blocks in Talbot-Jones 
rattler. 

For Description of a Pavement Testing Machine used by the National Physical Lab- 
oratory (Teddington, England), see 6th Annual Report of Road Board, 1916. 
A brief description is given in Report of New York Commissioner of Highways, 
1913. v. II, p. 120; also Mechanical Testing, by Batson and Hyde, v. I, 1922. 

Apparatus for Measuring the Wear of Concrete Roads, by A. T. Goldbeck; 
Jl. Agr. Research, Feb. 14, 1916. 

Tests of Concrete Road Aggregates, by J. P. Nash; 

Proc. Am. Soc. Testing Mat.. Part II. 1917. p. 394. 

Used specimen in form of annular ring similar to Shoop's tests. See dis- 
cussion by Mattimore, Abrams, and Goldbeck. 

Effect of Time of Mixing on the Strength and Wear of Concrete, by D. A. Abrams; 
Proc. Am. Concrete Inst., 1918. 
Canadian Engineer, July 25-Aug. 8, 1918. 
Wear tests on separately molded concrete blocks using Talbot-Jones rattler. 

Wear Resisting Values of Various Aggregates for Concrete Roads, by H. S. Mattimore; 
Engineering News-Record, May 2, 1918. 

Tests on special machine which produced impact blow on concrete surface 
through steel calks. 

Abrasion Tests of Concrete, by Giesecke and Finch; 
Bull. 1815, Univ. of Texas, p. 82, 1918. 

Records of Wear on Concrete Pavements, Hartford, Conn.; 
Engineering and Cement World, July 15, 1918. 

Wear-Resisting Values of Various Aggregates for Concrete Roads, by H. S. Matti- 
more; 

Eng. News-Rec, May 2, 1918. < 
Report of New York Commissioner of Highways, 1918, p. 62. 



Effect of Curing Condition of Concrete 



31 



Studying the Effect of Impact and Wear on Road Surfaces; 
Eng. News-Rec, Sept. 18, 1919, and April 8, 1920. 

Instrument for Measuring Wear of Concrete and Other Surfaces, by W. E. Rosen- 
garten; 
Public Roads, v. 2, p. 12, August, 1919. 

Testing Aggregates for Concrete Roads, by H. E. Breed; 
Eng. News-Rec, June 5, 1919. 

Impact Tests of Concrete Slabs and Wear Tests of Pavement Sections, by P. Hubbard; 
Public Roads, July, 1919. 



Impact Test on Concrete to Regulate Coarse 
for Highways, by H. S. Mattimore; 
Proc. Am. Soc. Testing Mat.. Part II. 



and Fine Aggregate Qualities and Mixes 
1920. p. 266. 
and Other Powdered Admixtures in Concrete, by D. A. 



Effect of Hydrated Lime 
Abrams; 
Proc. Am. Soc. Testing Mat., Part II, 1920. 

Gives results of wear tests of concrete containing various powdered admix- 
tures. 

Wear Tests of Slag Concrete, by Gray and Kellam; 
Concrete Highway Mag., Feb., 1920. 

New Laboratory Abrasion Test for Concrete, by C. H. Scholer; 
Eng. News-Rec. Sept. 22, 1921, p. 488. 
Chem. Abs., v. 16, p. 324, 1922. 

9-in. concrete spheres were tested in standard brick rattler. 

Wear Tests of Concrete, by D. A. Abrams; 
Proc. Am. Soc Testing Mat, 1921. 
Bull. 10, Structural Materials Research Lab., 1921. 

Gives results of about 7,000 wear tests of concrete made at Lewis Institute in 

Talbot-Jones rattler. 

Abrasion Machine for Testing Composition Floors (article on oxychloride cements) 
by M. Y. Seaton; 
Proc. Am. Soc. Testing Mat., 1921. 

Accelerated Wear Tests by the Bureau of Public Roads, by Jackson and Hogantogler; 
Public Roads, June, 1921. 
Eng. News-Rec, June, 1921. 

Practical Uses of Excess Sand in Concrete Mixtures, by R. W. Crum; 
Eng. News-Rec, p. 812, Nov. 17, 1921. 

Gives results of wear tests of concrete blocks made in Talbot- Jones rattler on 
specimens molded on 13 different road jobs in Iowa. 

State Highways of Calif., Report of Automobile Clubs, 1921. 

States that in pavements constructed of mixtures of adequate 
factory workmanship, wear may be neglected, p. 117. 

Results of Heavy Traffic on Pittsburgh (Calif.) Test Road, by C. Geiger; 
Eng. News-Rec, v. 88, p. 1066, June 29, 1922. 
Concrete, v. 21, p. 23, July, 1922. 

Bates Experimental Road, by C. Older; 

Proc. Am. Road Builder's Assn., 1922, p. 173. 

Traffic Tests of Bates Experimental Road, 
Eng. News-Rec, Aug. 10, 1922. 

Progress report at end of the 5th 
Division of Highways. 

Highway Research and What the Results Indicate, by A. T. Goldbeck; 
Proc. Am. Road Builder's Assn., 1922, p. 198. 



richness and satis- 



traffic run on 2-mile test road by Illinois 



Abrasion Tests of Stone, Etc. 



The original work of Deval in developing the abrasion test for crushed rocks for use 
in macadam road construction was described in Annales des Ponts et Chaussees, 
1879, and Bulletin du Ministere des Travaux Publics, 1881. 

Quality of Good Road Metals and Methods of Testing, by H. F. Reid; 
Maryland Geological Survey, p. 317, 1898. 

Sand-Blast as an Abrasive Agent for Testing Purposes, by M. Gary; 
Baumaterialeinkunde, v. 10. 
Table of results in Johnson's Materials of Const.. 4th ed.. 1898. 



32 



Structural Materials Research Laboratory 



Use of the Talbot-Jones Rattler for Paving Brick Tests. 

Eng. News, July 13, 1899, p. 30. 

Proc. Nat. Brick Mfrs. Assn., 1899, 1900 and 1901. 
U. S. Road Materials Laboratory, by Page and Cushman; 

Proc. Am. Soc. Testing Mat., 1903. 

Early history of tests of road materials in the United States. 
Testing Building Materials by the Sand-blast Method, by H. Burchartz; 

Engineering (London), Nov. 30, 1906. 
Strength and Wear of Building Stones, by A. Hanisch; 

Mitt. Techn. Gew-Mus., 1907. 

Compression Strength and Abrasion of Artificial Building Stones and Floor Cover- 
ings, by A. Hanisch; 
Mitt. Techn. Gew-Mus., 1908. 

Acceptance of Stone for Use on Roads Based on Standard Tests, by R. S. 

Greenman; 

Proc. Am. Soc. Testing Mat., v. 8, 1908. 
Standard Abrasion Test for Road Materials, 

Proc. Am. Soc. Testing Mat., v. 8, 1908. 

Describes Deval abrasion test for crushed rocks. 

Testing Paving Stone with the Sand-Blast Machine, by M. E. H. Tjaden; 

De Ingenieur, July 16, 1910. 
Rattler Tests for Paving Brick, 

Munic. Jl., Nov. 16, 23, 1910. 
Note on Appliances for Testing Paving Setts, by Labordere and Anstett; 

Proc. 6th Cong. Int. Assn. Testing Materials, 1912, 2nd Section. 

Methods of Testing Road Materials in the Netherlands, by M. E. H. Tjaden; 
Proc. 6th Cong. Int. Assn. Testing Mat., 1912, 2nd Section. 

Brief reports on testing road materials in Austria, Belgium, Denmark and 
Norway in same volume. 

Physical Tests of Broken Stone Railroad Ballast, by Goldbeck and Jackson; 
Proc. 6th Cong. Int. Assn. Testing Materials, 1912. 

Comparison between Rattler Test and Sand-blast Test for Paving Brick, by Edward 

Orton, Jr.; 

Trans. Am. Ceramic Soc, v. XIV. p. 180, 1912. 
Relation between the Tests for the Wearing Qualities of Road-Building Rocks, by 

L. W. Page; 

Proc. Am. Soc. Testing Materials, 1913. 
Rattler Test Made on Brick Obtained from Paved Street, by G. H. Brown; 

Jl. Am. Ceramic Soc, p. 364, 1914. 
Relation between Properties of Hardness and Toughness of Road-Building Rock, by 

Hubbard and Jackson; 

Jl. Agr. Research, Feb. 7, 1916. 

Use of Slotted Cylinder for Deval Abrasion Test of Rocks; 
Report of New York Commissioner of Highways, 1917. 

Methods and Results of Physical Tests of Rocks for Road-Building, 
U. S. Bureau of Chem. Bull. 79, 1903; 
Bureau of Pub. Roads, Bull. 44, 1912. 
Dept. of Agr. Bull. 314. 1915; 347. 1916; 537. 1917; and 670. 1918. 

Abrasion Test for Gravel Aggregate, by A. S. Rea; 
Concrete Highway Magazine, June, 1918. 
General Specifications for Materials, Ohio State Highway Department, Columbus. 

Abrasion Test for Stone, Gravel and Similar Aggregate, by H. H. Scofield (Dis- 
cussion by H. S. Mattimore) ; 
Proc. Am. Soc. Testing Materials, Part II, 1918. 

Standard Deval Abrasion Test for Rocks, by F. H. Jackson; 
Proc. Am. Soc. Testing Mat., Part II, 1920. 
Public Roads, July, 1920. 

Causes for error are discussed and methods of avoiding them given. 

Standard Method of Test for Abrasion of Road Material; 

Standards Am. Soc. Testing Mat., p. 710, 1921. 
Standard Rattler Test for Paving Brick; 

Standards Am. Soc. Testing Mat., p. 567, 1921. 

Impact Test for Gravel, by F. H. Jackson; 

Proc. Am. Soc. Testing Mat., Part II, 1922. 
Selection of Mineral Aggregate for Concrete Roads, by D. A. Abrams; 
Proc. Am. Road Builders' Assn., p. 126, 1922. 

Gives results of abrasion tests in Deval machine by four different methods 
and corresponding strength and wear of concrete. 



Effect of Curing Condition of Concrete 33 

Effect of Consistency of Concrete on Strength and Other Properties 
and Method of Measuring Consistency. 

Practical Treatise on Limes, Hydraulic Cements and Mortars, by Q. A. Gillmore; 
Van Nostrand Co., 1873. 

Gillmore concludes that an excess of water is better than a deficiency (Par. 
446). Quotes tests from Vicat which showed rapid reduction in strength of 
concrete with increase in quantity of mixing water (Par. 512). 

Relative Strength of Wet and Dry Concrete, by J. W. Sussex; 
Technograph (Univ. of 111.), 1902-3. 
Eng. News, July 16, 1903. 

Strength of Concrete as Affected by Different Percentages of Water, by Doyle and 
Justice ; 
Eng. News, July 30, 1903. 

Tests of Concrete, by Geo. W. Rafter; 
Municipal Engineering, Jan., 1903. 

Dry and Plastic Mortars, by R. Feret; 
Cement Age, v. 2, p. 185, 1905. 

Consistency of Concrete, by S. E. Thompson; 
Eroc. Am. Soc. Testing Materials, 1906. 

Influence of Proportion of Water on the Compressive Strength of Cement Mortar 
and Concrete, by Brabandt; 
Engineering (London), May 15, 1908. 
Concrete Eng., v. 3, p. 316, 1908. 

Consistency of Concrete; 

Trans. Concrete Inst. (London), June, 1909. 

Gives quantity of water to be added to concrete. 

Effect of Excess Water on Strength and Permeability of Concrete and Neat Cement 
(Metamorphism of Portland Cement), by H. B. Pacini; 
Annals N. Y. Acad. Sci., No. 22, p. 194, 1912. 

Consistency of Concrete; 

Eng. Rec, v. 65, p. 185, 1912. 

Gives recommendations regarding consistency of concrete. 

Excess Water in Cement Mixtures, by H. B. Pacini and others; 
Concrete-Cement Age, Dec, 1912. 

Consistency of Concrete; 

Trans. Concrete Inst. (London), v. 4, Part 1, p. 76, 1912. 

Replies to inquiry on the consistency of concrete, and conclusions of the 
Committee. 

Effect of Too Much Water in Mixing Concrete, by C. J. Robinson; 
Eng. News, May 22, 1913. 

Method and Apparatus for Determining Consistency, by C. M. Chapman; 
Proc. Am. Soc. Testing Mat., v. 13, p. 1045, 1913. 

Describes apparatus for testing consistency of cement and concrete, limits for 
each method and comparison of results with tests of the Vicat needle. 

Effect of Consistency on Strength of Concrete. 

Jl. Am. Concrete Inst., October-November, 1914, p. 436. 

Abs. Johnson's Materials of Construction, 5th Ed., p. 469, 1919. 

Report of tests made by several colleges cooperating with Inst. Committee. 

Consistency of Concrete; 

Trans. Concrete Inst. (London), v. 5, Part 2, p. vii, 1914.. 

Gives changes in proposed specifications for consistency of concrete. 

Experimental Determination of the Effect of Varying the Percentage of Water in 
Concrete, by R. K. Skelton. 
Proc. Conn. Soc. Civil Eng., 1914. 

Permeability Tests of Gravel Concrete, by M. O. Withey; 
Jl. West. Soc. Eng., Nov., 1914. 

Effect of consistency of concrete on permeability. 

Water the Chief Factor in Making Good Concrete, by N. C. Johnson; 
Eng. Rec, Dec. 30, 1916. 

Strength and other Properties of Concrete as Affected by Materials and Methods of 
Preparation, by R. J. Wig, C. M. Williams, and E. R. Gates; 
Technologic Paper No. 58, U. S. Bureau of Standards, 1916. 

Effect of Grading of Sands and Consistency of Mix upon the Strength of Plain and 
Reinforced Concrete, by L. N. Edwards; 
Proc. Am. Soc. Testing Materials, Part II, 1917. Also Part II, 1918. 



34 



Structural Materials Research Laboratory 



Tests of Slabs to Determine the Effect of Removing Excess Water, by A. N. Johnson; 
Proc. Am. Soc. Testing Materials, Part II, 1917. 

Excess water removed by roller; tests made at Lewis Institute. 

Concrete Consistency Measured by Simple Field Test, by H. A. Thomas; 
Eng. News-Rec, v. 78, p. 244, 1917. 

Recommends use of angle of repose of freshly-mixed concrete as measure of 
consistency; gives results of tests. 

Effect of Fineness of Cement, by D. A. Abrams; 

Proc. Am. Soc. Testing Mat., v. 19, Part II, 1919. 

Tests made on concrete of wide range of consistencies. 

Effect of Curing Condition on the Wear and Strength of Concrete, by D. A. Abrams; 
Proc. Am. Ry. Eng. Assn., v. 20, 1919. 
Bull. 2, Structural Materials Research Lab., 1919. 

Compression and wear tests on concrete of a wide range of consistencies. 

Consistency of Portland Cement, Mortar and Concrete, by H. G. Lloyd; 
Surveyor (London), May 7, 1920; v. 57, p. 401, 1920. 
Eng. and Contr., June 30, 1920. 

Concrete and Const. Engr., v. IS, p. 411-415, June, 1920. 
Engineering, v. 109, p. 587, April 30, 1920. 

Paper before Concrete Inst, gives explanation of the "Boulogne" method of 
proportioning mixing water, which consists of forming a ball of cement with 
enough water that it will retain shape when dropped 20 in. 
Measuring Flowability of Concrete by Flow-Table, by G. M. Williams; 
Concrete, v. 16, p. 274, June, 1920. 
Canadian Eng., v. 38, p. 545, June 10, 1920. 
Eng. News-Rec, p. 1044, May 27, 1920. 
Chem. Abs., July 10, 1920. 
Apparatus for Determining the Consistency of Concrete, by F. L. Roman; 
Eng. & Contr., v. 53, p. 240. March 3, 1920. 

Describes use of truncated cone for slump test. 
Measurement of Plasticity of Mortars and Plasters, by W. E. Emley; 
Tech. Paper 169. U. S. Bureau of Standards. 1920. 
Abs. Jl. Am. Ceramic Soc, p. 775, September, 1920. 

Describes new apparatus which produces a trowelling effect by means of a 
rotating metal disc 
Workability of Concrete, 

Concrete, p. 34, July, 1920. 
Tentative Specifications for Workability of Concrete for Concrete Pavements; 
Proc. Am. Soc. Testing Mat., v. 20, Part I, p. 692, 1920. 

Apparatus and method for determining slump is described; method slightly 
revised in 1922. 
Effect of Hydrated Lime and Other Powdered Admixtures in Concrete, by D. A. 
Abrams; 

Proc. Am. Soc Testing Mat.. Part II. 1920. 
Bull. 8, Structural Materials Research Lab., 1920, p. 60. 

Gives results of tests on concrete of wide range in consistency; flow-table 
described. 
Description and Photograph of Flow-Table, (in paper on Modulus of Elasticity of 
Concrete), by G. M. Williams; 

Proc. Am. Soc. Testing Mat, v. 20, Part 2, p. 243, 1920. 
Abs. Concrete, June, 1920, p. 274. 
Tests of a Concrete Mixer, by W. K. Hatt; 
Proc. Am. Concrete Inst., p. 47, 1921. 

Discusses effect of time of mixing on consistency. 
Consistency of Starch and Dextrin Pastes, by Herschel and Berquist; 

Jl. Ind. & Eng. Chem., v. 13, p. 703, August, 1921. 
Effect of Consistency of Concrete, 

Proc. Am. Soc. Testing Mat., v. 21, p. 301, 1921. 

Consistency was measured by flow-table; tests made by Delaware State High- 
way Department. 
Comparison of Results of Slump Test and Flow-Table in the Measurement of the 
Consistency of Concrete, by W. L. Schwalbe; 
Proc. Am. Soc. Testing Mat., v. 21, p. 983, 1921. 
Concrete & Const. Eng., August, 1921. 
Chem. Abs., v. 16, p. 1645, 1922. 

Tests show how consistency varies with time of mixing; concludes that the 
flow-table is more reliable then the slump test for measuring consistency. 
Time of Set of Concrete, by W. Davis; 

Proc. Am. Soc. Testing Mat., v. 21, p. 995, 1921. 
Chem. Abs., v. 16, p. 1644, 1922. 

Data and examples of use of the flow-table in determining some of the factors 
influencing the set of concrete. 



Effect of Curing Condition of Concrete 



35 



Proposed Tentative Methods of Making Concrete Compression Tests, 
Proc. Am. Soc. Testing Mat., v. 21, p. 581, Part II, 1921. 

Describes slump test and flow-table for consistency of concrete. 
Study of Elastic Viscous Deformation, by P. G. Nutting; 
Proc. Am. Soc. Testing Mat., v. 21, p. 1162, 1921. 

Method of testing pitch, asphalt, etc., for viscousness and elastic yield, by the 
falling ball method and rate of flow through a tube. 
Quantities of Materials for Concrete, by Abrams and Walker; 
Bull. 9, Structural Materials Research Lab., 1921, p. 7. 
Slump and flow tests described and compared. 
Testing Consistency of Calcined Gypsum; 

Proc. Am. Soc. Testing Mat., v. 21, p. 594, 1921. 

Describes use of Southard Viscosimeter; field method described on p. 596. 
Variation in the Effect of Rodding Concrete, by F. E. Giesecke; 

Proc. Am. Soc. Testing Mat., v. 21, p. 1008, 1921. 
La Plasticite des Mortiers et sa Mesure; 

Rev. des Mat. des Const., No. 153, p. 112, June, 1922. 

Defines plasticity; tells of old methods of measuring it, and describes Emley's 
method from Tech. Paper 169, U. S. Bureau of Standards, 1920. 
Relation between Voids and Plasticity of Cement Mortars at Different Relative Water 
Content, by Richert and Bauer; 

Proc. Am. Soc. Testing Mat., v. 22, Part II, 1922. 
Eng. News-Rec, v. 89, p. 109, 1922. 

To Avoid Variable Concrete Due to Variable Sand Wetness, by R. L. Bertin; 
Eng. News-Rec, v. 89, p. 1047. June, 1922. 

Proposes inundating sand before dumping in mixer; thus keeping moisture 
content constant. 
Consistency of Concrete, by H. O. Weller; 
Ferro-Concrete, v. 13, p. 299, May, 1922. 

Method of measuring consistency by means of flow-table is described. 
Plasticity of Clays, by F. P. Hall; 

Jl. Am. Ceramic Soc, v. 5, p. 347, June, 1922. 

Term "plasticity" is discussed, methods of measuring, the use of the Bingham 
plastometer, and need of more efficient method of measuring plasticity. 
Mechanism of Plasticity from Colloid Standpoint, by G. A. Bole; 
Jl. Am. Ceramic Soc, v. 5, p. 469, Aug., 1922. 

Gives theory of plasticity and method of measuring. 
Fluidity and Plasticity, by E. C. Bingham; 
McGraw-Hill Book Co., 1922, 440 pages. 

Largely theoretical; gives extensive bibliography. 
Tentative Specifications for Workability of Concrete for Concrete Pavements, 
Prac Am. Soc. Testing Mat., Part I, 1922. 
Based on slump test using truncated cone. 
Flexural Strength of Plain Concrete, by D. A. Abrams; 
Proc. Am. Concrete Inst., v. 18, 1922. 
Bull. 11, Structural Materials Research Lab., 1922. 

Tests made on concrete of wide range of consistencies. 
Compression Tests of Concrete Made in Cooperation with Committee C-9. 
Proc. Am. Soc. Testing Mat., Part I, 1922. 

Summaries of tests using concrete of different consistencies, gradings of 
aggregates, etc., made by Philadelphia Department of Public Works, Uni- 
versity of Texas, University of Toronto, and Hydro-Electric Power Commis- 
sion of Ontario. 

Effect of Curing Conditions of Concrete 



Cements Setting in Air and in Water, 

Tests of Metals, p. 422, 1902. 
Effect of Steam Curing on the Crushing Strength of Concrete, by R. F. Havlik; 

Eng. News, Sept. 5, 1907. 

Tests made at Lewis Institute, with conclusions. 
Tests to Determine the Effects of Frost on Concrete and Methods of Concrete Work 

in Freezing Weather, by J. H. Chubb; 

Eng. & Contr., Nov. 23, 1910. 
Tests of Mortar and Concrete Under the Influence Alternately of Frost and Thaw, 

by H. Burchartz; 

Mitt. kgl. Materialpruf, No. 5, 1910. 
Effect of High Pressure Steam on the Crushing Strength of Portland Cement Mortar 

and Concrete, by R. J. Wig; 

Proc. Am. Soc. Testing Mat., Part II, p. 580, 1911. 

Tech. Paper No. 5, U. S. Bureau of Standards, 1912. 



36 



Structural Materials Research Laboratory 



Effect of Curing Condition of Concrete. 

Jl. Am. Concrete Inst., p. 436, Oct.-Nov., 1914. 
Tests made at University of Illinois. 
Influence of Temperature on the Strength of Concrete, by A. B. McDaniel; 

Bull. 81, Eng. Exp. Sta., Univ. of 111., 1915. 

Proc. Am. Concrete Inst., p. 241, 1916. 
Effect of Water on the Strength of Concrete, by D. A. Abrams; 

Concrete Highway Mag., April, 1917. 

Concrete & Constr. Eng., Sept., 1921, p. 594. 
Recommended Practice for Concrete Road and Street Construction, 

Proc. Am. Concrete Inst., 1918. 
Effect of Age and Condition of Storage on the Strength of Concrete, by H. F. 

Gonnerman; 

Proc. Am. Concrete Inst., 1918. 
Relation Between Methods of Curing Standard Concrete Test Specimens and Their 

Compressive Strength at 28 Days, by H. W. Green; 

Proc. Am. Soc. Testing Mat., Part II, 1919. 
Effect of Curing Condition on the Wear and Strength of Concrete, by D. A. Abrams; 

Proc. Am. Ry. Eng. Assn., v. 20, 1919. 

Bull. 2, Structural Materials Research Lab., 1919. 
Ten- Year Tests Showing the Effect of Age and Curing Conditions on the Strength of 

Concrete, by M. O. Withey; 

Wis. Eng., Nov., 1920. 

Abs. Eng. & Cont., Nov. 24, 1920. 
Proper Finishing and Protection Against Rapid Drying, Important Features of Con- 
crete Floor Construction, by J. E. Freeman; 

Eng. & Contr., v. 57, p. 622, June 28, 1922. 

Recommends curing floors under moisture the same as concrete roads. 
Calcium Chloride in Concrete Highway Construction, by Piepmeier and Clemmer; 

Eng. News-Rec, v. 88, p. 409, March 9, 1922. 

Successful Methods, June, 1922. 

Calcium chloride used in substitute for damp earth, etc., for curing of con- 
crete highways; gives results of transverse tests on plain concrete beams made 
by Illinois Division of Highways. 



LIST OF PUBLICATIONS OF THE 
STRUCTURAL MATERIALS RESEARCH LABORATORY 



Circular 1.— Colorimetric Test for Organic Impurities in Sands, by Duff A. 
Abrams and Oscar E. Harder (1917). Out of Print. 

(For a more recent discussion of this subject see, "Abrams-Harder Field Test 
for Organic Impurities in Sands," Proc. Am. Soc. Testing Mat., 1919, Part I; 
also "Tentative Method of Test for Organic Impurities in Sands for Con- 
crete," Proc. Am. Soc. Testing Mat., 1921.) 

Bulletin 1. — Design of Concrete Mixtures, by Duff A. Abrams (1918). 

Bulletin 2. — Effect of Curing Condition on the Wear and Strength of Concrete, 
by Duff A. Abrams (1919). 

Reprinted from the Proc. Am. Railway Eng. Assn., Vol. 20, 1919. 

Bulletin 3. — Effect of Vibration, Jigging and Pressure on Fresh Concrete, by 
Duff A. Abrams (1919). 
Reprinted from the Proc. Am. Concrete Inst., Vol. XV, 1919. 

Bulletin 4.— Effect of Fineness of Cement, by Duff A. Abrams (1919). 

Reprinted from the Proc. Am. Soc. Testing Mat., Vol. XIX, Part II, 1919. 

Bulletin 5. — Modulus of Elasticity of Concrete, by Stanton Walker (1920). 

Reprinted from the Proc. Am. Soc. Testing Mat.. Vol. XIX. Part II, 1919. 

Bulletin 6. — Effect of Storage of Cement, by Duff A. Abrams (1920). 

Bulletin 7.— Effect of Tannic Acid on the Strength of Concrete, by Duff A. 
Abrams (1920). 

Reprinted from the Proc. Am. Soc. Testing Mat., Vol. XX, Part I, 1920. 

Bulletin 8. — Effect of Hydrated Lime and Other Powdered Admixtures in 
Concrete, by Duff A. Abrams (1920). 

Reprinted from the Proc. Am. Soc. Testing Mat., Vol. XX, Part II, 1920. 

Bulletin 9. — Quantities of Materials for Concrete, by Duff A. Abrams and 
Stanton Walker (1921). 

Bulletin 10. — Wear Test of Concrete, by Duff A. Abrams (1921). 

Reprinted from Proc. Am. Soc. Testing Mat., Vol. 21, 1921. 



Bulletin 11. — Flexural Strength of Plain Concrete, by Duff A. Abrams (1922). 

Reprinted from the Proc. Am. Concrete Inst.. Vol. XVIII. 1922. 



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